A Chery 1.5 car with a mileage of about 80 thousand km. User response: when the vehicle starts to use, the clutch pedal can not fully start the car up. After receiving the car, I was told that the coach was used as a trainer for about 1 years. According to experience, it is judged that the excessive wear of the clutch results in the lack of joint engagement, resulting in the interruption of power transmission and the clutch skidding. In the process of automobile use, as the use of the clutch is quite frequent, with the increase of the mileage of the car, the parts of the clutch are inevitably worn or damaged, resulting in the failure of the technical state of the clutch. In practice, the main failures of clutch are skid, incomplete separation, trembling and abnormal sound. Clutch skidding means that when the clutch is completely relaxed and the drive system is not overloaded, when the clutch is in a state of combination, the main and the driven disc can not reach the constant speed, that is, there is a relative sliding, and the engine's power can not be completely passed or even broken. Fault reason: clutch skid is one of the common faults in the use of clutch. The causes of clutch skidding are: (1) the clutch pedal has no free travel; (2) the friction disc of the clutch disc is worn thin, hardened, corroded, riveted or stained with oil; (3) the clutch pressure plate is too thin or pressure disc, flywheel deformation; (4) the clutch pressure spring is overheated or broken; (5) (5) The coupling lever adjustment is too high; (6) the loosening of the clutch cover and the connecting bolt of the flywheel; (7) the diaphragm spring of the diaphragm spring clutch is insufficiently elastic or the diaphragm is broken. Troubleshooting: initially determined that the clutch disc wear too thin, decided to replace the clutch. The specific steps are as follows. 1. clutch dismantling the trouble car into the middle of the lift, supporting 4 stents and lifting the ground. (1) remove the wheels on both sides of the front axle and take out both sides of the transmission shaft. (2) remove the outer connector of the transmission and clutch. 1) dismantle the battery positive pole and the starter connecting wire; 2) pull out transmission gear shift and pick up line lock, remove pull wire; 3) remove all sensors, including, odometer sensor and inverted alarm sensor. (3) dismantle the clutch sub pump. (4) loosening the thermostat. To help lift the transmission. (5) remove the connecting bolts from the upper part of the transmission to the upper part of the flywheel housing, raise the vehicle to the high position, and then remove the connecting bolts from the bottom of the transmission to the bottom of the flywheel housing. (6) lifting the bottom of the transmission with a jack. Remove transmission support connection bolts and lower transmission. (7) dismantle the clutch assembly. It is found that the rear side of the clutch friction plate is worn to the rivet exposure (as shown in Figure 1), and the pressure plate indicates that the tension is serious and the clutch assembly is replaced by the first fault diagnosis. During the dismantling process, it was found that the left half axle steering knuckle and the clutch release bearing were all abnormal sound and replaced together. 2. structure analysis clutch is a component connecting the engine and transmission to separate or join the dynamic connection between them. The main functions are: make the engine and the transmission line join gradually, ensure the car to start smoothly; temporarily cut off the connection between the engine and the transmission system, facilitate the starting of the engine and the transmission of the transmission; the main and the driven parts can be relatively slippery, absorb part of the energy and prevent the damage of the machine parts from the overload. Chery Qiyun 1.5 car is a diaphragm spring pressed friction clutch, its working principle is shown in Figure 2. When the clutch cover is not fixed to the flywheel, the diaphragm spring is in free state, and there is a certain distance between the cover and the flywheel joint surface, as shown in Fig. 2 (a). When the clutch cover is fixed to the flywheel, the clutch cover pushes the diaphragm spring forward and presses the disc tightly on the rear end of the flywheel (the cone angle becomes smaller), when the clutch is engaged, such as Figure 2 (b). When the clutch is separated, the bearing is moved forward, and the diaphragm spring is anti conical. Under the action of the separating hook, the pressure plate moves backward from the driven plate. The clutch works with the principle of friction. The maximum torque that the friction clutch can transfer depends on the maximum static friction torque between the friction surfaces, which is determined by the maximum pressure between the friction surfaces and the size and properties of the friction surface. In the process of use, because of the wear of the friction disc, the maximum pressure between the friction surfaces decreases gradually, and the friction surface becomes more and more smooth and the friction coefficient decreases. Thus the maximum torque of the friction clutch can be reduced and the clutch slip fault is produced. 3. clutch mounting (1) install new clutch assembly. Pay attention to the leveling of the friction plate. (2) lift the transmission, first fix the bolt with the flywheel housing, then fix the support. (3) install the half shaft and the wheel. Attention should be paid to the replacement of new tennis cages. Special grease should be added after universal joints. (4) connect the sensor and transmission cable and fix it. (5) installation of clutch sub pump. (6) install starter and connect the battery positive pole power line. (7) connect the power line of the positive pole of the battery. (8) add enough coolant. (9) test the car. The start is normal. The follow-up was normal and the failure was excluded.